The present invention relates to a mounting assembly for a roller blind and the like. More particularly this invention concerns such an assembly which allows the roller blind carried thereby to be arrested in any of a multiplicity of positions.
Roller blinds are frequently mounted at the top of the window or at the edge of the aperture across which the blind moves. Such a device typically includes some kind of frame or housing, a shaft rotatable relative to this housing, and means interconnecting the shaft and the housing in order to allow the blind to be arrested at any of a multiplicity of positions.
In the most common of such arrangements a spring is provided in the rod or shaft carrying the roller blind and means is provided which includes a centrifugally outwardly swingable pawl that is urged radially inwardly by means of a very weak spring. This pawl is carried on the shaft so that it is rotated as the blind is raised and lowered, and there is provided a non-rotatable toothed wheel fixed relative to the shaft with which the pawl can engage in order to arrest rotation of the shaft relative to the housing. The pawl, spring, and teeth of the wheel in the rod are so arranged that the rod can always move in a direction corresponding to unwinding of the blind from this rod, but the pawl can block movement in the opposite direction. With such an arrangement, therefore, the pawl does not engage the teeth so long as the rod is rotating relatively rapidly relative to the housing, as centrifugal force holds the pawl out of engagement with the teeth. When the rod is rotated relatively slowly, however, the pawl can engage. Thus to raise the blinds the user must first jerk it sharply downwardly and then move it rapidly upwardly in order to maintain sufficient rotational speed to hold the pawl back.
Such an arrangement often has a relatively limited service life. In particular when used with relatively heavy slat-type roller blinds or the like such an arrangement frequently wears out in a very short time. In addition it is impossible with such devices to have a stepless positioning of the blind, as the blind rod can only be arrested in a position corresponding to interfitting of the pawl with one of the teeth on its non-rotatable wheel.